The present invention relates to a novel thin film magnetic head, a recording/reproduction separation type head using the thin film magnetic head, and a magnetic recording and reproducing apparatus.
A thin film magnetic head for a magnetic disk apparatus is formed on a slider held above a disk which rotates at high speed. The magnetic head has a magnet pole layer in the form of a thin film made of a ferromagnetic material. On an air bearing surface (ABS), a lower magnetic pole layer and an upper magnetic pole layer are provided on and under a gap layer. The upper and lower magnetic pole layers of the recording head are in contact with each other in the rear part of the gap. In order to increase the recording density, it is necessary to write a large amount of data on the surface of a magnetic disk. For this purpose, it has been proposed to narrow the track width, thereby increasing the recording density. A method which provides a thin film magnetic head having a width at the magnetic pole end, that is, a track width, of 2 xcexcm or narrower is described in Japanese Patent Application Laid-Open No. 7-296328. According to the method described in this publication, when a magnetic film is formed by plating, a silicon dioxide layer is used as a plating frame. It is described in the publication that the magnetic pole layers from the ABS to the zero throat level in the rear part are wider than a magnetic pole end layer and are in parallel, and that a parallel path is formed for receiving and transferring the magnetic flux from/to the magnet pole end region, thereby enhancing the magnetic flux transmitting ability. Further, the shape of the upper magnetic film (shown by P2(T) in FIG. 24 and P2 in FIG. 25) is clearly shown in the head construction diagram of FIGS. 24 and 25 of the publication. The cross-sectional area of the upper magnetic film is constant, when it is seen from the air bearing surface at the gap depth position (upper part of the frame).
It is an object of the invention to provide a thin film magnetic head with less blur having a high recording magnetic field, and a recording/reproduction separation type magnetic head using the thin film magnetic head as well as a magnetic recording and reproducing apparatus.
It is another object of the invention to provide a high-frequency driven magnetic head having a magnetic pole width of 1 xcexcm or narrower and a magnetic recording and reproducing apparatus which uses the magnetic head and has a very high recording density.
According to the invention, there is provided a thin film magnetic head having an upper magnetic film and a lower magnetic film disposed on either side of a non-magnetic gap film, wherein on at least one of the upper and lower magnetic films, an upper end part magnetic film is formed on the upper magnetic film and a lower end part magnetic film is formed on the lower magnetic film via the magnetic gap at the ends in which the magnetic gap is formed on the magnetic gap side.
The invention is also characterized in that a cross-sectional area parallel to the air bearing surface of at least one of the upper and lower end part magnetic films is smaller than the cross-sectional area of the upper and lower magnetic films in a part having the magnetic gap; the track width of at least one of the upper and lower end part magnetic films is narrower than the track width of the upper magnetic film and that of the lower magnetic film; and at least one of the upper and lower end part magnetic films is projected more than the upper and lower magnetic films on the air bearing surface toward the air bearing surface side.
According to the invention, the thin film magnetic head as mentioned above is characterized by either one of the following two features or the combination thereof; i.e., (1) the fact that each of the upper and lower end part magnetic films is constructed by a plated magnetic film having a saturated magnetic flux density of 1.5 tesla or higher and the upper magnetic film is formed by plating or sputtering so as to have the width wider than a frame width of the plated magnetic film and a specific resistance of 50 xcexcxcexa9xc2x7cm or higher; and (2) the fact that the upper and lower end part magnetic films have the same track width, an upper shield film for magnetically shielding the upper magnetic film and a magnetic resistive film has a width wider than the track width, and the upper magnetic film is constructed by one or a plurality of multilayered magnetic films.
According to the invention, there is provided a recording/reproduction separation type magnetic head, in which a recording head for writing information and a reproduction head for reading information are integrally formed, wherein the recording head, is constructed in the form of the above mentioned thin film magnetic head.
In the above mentioned recording/reproduction separation type magnetic head according to the invention, the reproduction head includes a ferromagnetic layer having a magnetic resistive effect and an antiferromagnetic layer which is closely attached to the ferromagnetic layer and allows the ferromagnetic layer to exhibit one-way anisotropy, and the antiferromagnetic layer is made of a Crxe2x80x94Mn alloy.
According to the invention, a magnetic recording/reproduction apparatus, which comprises a thin film magnetic disk, on which information is recorded, rotating means for the thin film magnetic disk, a recording/reproduction separation type magnetic device which is attached to a floating type slider and has a recording head for writing information and a reproduction head for reading information, and moving means for supporting the floating type slider and accessing the thin film magnetic disk; wherein, the magnetic disk, rotating at 4000 rpm or higher for recording and reproduction and having a recording frequency of 45 MHz or higher, is characterized in that it is accessed by a recording/reproduction separation type magnetic head constructed using the foregoing recording/reproduction separation type magnetic head.
Preferably, the invention is applied to a magnetic disk apparatus having a recording density of 4 Gb/in2 or higher When a recording head is seen from the air bearing surface, as shown in FIG. 1, the track width of the magnetic film 1 above the gap is narrowed relative to a track width Tw near the gap, and the upper end part magnetic film 16 shown in FIG. 2 is widened on both sides of the track by the length t of the overhang. A frame member having an undercut is fabricated by the combination of irradiation of ultraviolet rays and far ultraviolet rays and two stages of development of a two-layered film using a photo resist and polydimethylglutarimide; a gap film is formed between the photo resist layers; and the lower magnetic film is undercut.
When a magnetic head having the structure, as shown in FIG. 3 according to the invention, is fabricated, since a frame member made of silicon dioxide or the like is not used, the wear resistance and an apparatus for forming the frame member become unnecessary. Since the upper magnetic film 11 is not exposed to the air bearing surface, as shown in FIG. 3, there is little leakage of the magnetic flux from the upper magnetic film to the air bearing surface, so that blur on the medium can be reduced. As shown in FIG. 6, when the shape of the upper magnetic film is changed in the throat height, the cross-sectional area on the air bearing surface side parallel to the air bearing surface is reduced, which is enlarged from the middle of the throat height. Consequently, the magnetic field which leaks from the upper magnetic film 11 to the air bearing surface is reduced, and the magnetic field which leaks from the upper magnetic film 11 via the upper end magnetic film 17 can be increased. The head can be used for a magnetic recording apparatus of high recording density having a surface recording density of 4 Gb/in2 or higher. It is very important for the narrow track head to have a reduced overhang t near the air bearing surface of the upper magnetic film. In accordance with the invention, by setting the overhang at five times or smaller of the thickness of the gap film 17, the blur is reduced.
As an example, in the case where the track width (Tw) is 1.0 xcexcm, the thickness (pu) of the upper magnetic film is 4 xcexcm and the thickness of the gap film is 0.2 xcexcm, the relation between the magnetic field H which leaks from the end of the upper magnetic film 11 and the overhang t is as shown in FIG. 7. The smaller the leakage magnetic field is, the better. However, as the overhang t is reduced, the magnetic field strength near the gap on the air bearing surface decreases when the thickness of the upper magnetic film is made constant. In order to increase the magnetic field strength and to reduce the leakage magnetic field, a range of t in which Hxe2x89xa61000 Oe in this case, that is, txe2x89xa61 xcexcm, is desirable and a value of five times as thick as the thickness (0.2 xcexcm) of the gap film or smaller is desirable. In order to enhance the magnetic field strength when txe2x89xa61 xcexcm, it is sufficient to increase the thickness of the upper magnetic film 11. When the thickness of the upper magnetic film 11 is increased, the shape and the accuracy of a plating frame for forming the upper magnetic film 11 become a problem. That is, when the plating frame becomes thick, it is difficult to control the shape thereof and the accuracy of positioning relative to the magnetic film (upper end part magnetic film 16) thereunder becomes a problem. Consequently, from the point of view of the shape and the accuracy of the plating frame, it is difficult to realize t=0 xcexcm. It is preferable to select t=0.05 to 0.1 xcexcm and increase the thickness of the upper magnetic film 11. The above described example relates to the case where the upper magnetic film 11 is spaced from the air bearing surface by 10 nm. However, if the upper magnetic film 11 is spaced from the air bearing surface by more than 10 nm, the magnetic field on the air bearing surface from the upper end part magnetic film is reduced. By changing the structure of the conventional recording head, as shown in FIG. 2, according to the structure of the invention, as shown in FIG. 3, the erasure of recording data and undesirable influence on adjacent tracks due to the magnetic field leaking from the upper end part magnetic film are prevented. Effects similar to those of the structure as shown in FIG. 3 can be obtained by enlarging the cross-sectional area of the upper magnetic film 11 in a position less than the gap depth (the width of the gap film in FIG. 3 from the air bearing surface) which is spaced from the air bearing surface and by reducing the cross-sectional area on the air bearing surface.
According to the invention, a magnetic pole end part of the recording head of the thin film magnetic head is fabricated by frame plating. That is, the three kinds of films which make up the upper end part magnetic film 16, the gap film 17 and the lower end part magnetic film 18, as shown in FIGS. 2 and 3, are plated by using the same frame. The upper magnetic film 11 as shown in FIGS. 2 and 3 is in contact with the upper end part magnetic film 16 on the air bearing surface side. According to the conventional structure, the shape of the upper end part magnetic film 16 is as shown in FIG. 2 in cross section in the vertical direction to the air bearing surface and is as shown in FIG. 4 when seen from above the film face. As shown in FIG. 4, the shape of the gap film 17 and that of the upper end part magnetic film 16 are the same until the gap depth (frame end) from the air bearing surface, and the cross section parallel to the air bearing surface is the same from the air bearing surface to the gap depth (cross section of the location where the gap film exists). In contrast to the conventional shape as indicated above, as shown in FIG. 5 or 6, the cross-sectional area of the upper end part magnetic film 16 on the air bearing surface side is reduced, whereby the magnetic field leaking from the upper end part magnetic film 16 is reduced on the air bearing surface, so that the recording magnetic field becomes sharp, the magnetic field distribution of the track edge becomes sharp, and the background is reduced.
As an antiferromagnetic film, an oxide nickel film, an iron-manganese alloy thin film, a chromium-manganese, chromium-manganese-platinum, chromium-aluminum alloy film or the like can be used. A hard magnetic film, such as a ferromagnetic cobalt-platinum, cobalt-chromium-platinum or iron-cobalt-terbium alloy film can be also used. The hard magnetic film is a magnetic film whose magnetization is not easily changed by an external magnetic field. Since the direction of magnetization is hardly changed even when a magnetic field of 50 oersted, where the coercive force is for example 100 oersted or larger, is applied, effects similar to those of the antiferromagnetic film can be obtained. That is, as long as a film has a characteristic that one-way anisotropy by a switched connection bias can be applied, when the film is formed so as to be closely attached to another magnetic film, the film does not always have to be antiferromagnetic. It is preferable to use a film generally called a bias film.
As the magnetic film, it is preferable to use an alloy of Ni 70 to 95 at %, Fe 5 to 30 at %, and Co 1 to 5 at % or an alloy of Co 30 to 85 at %, Ni 2 to 30 at % and Fe 2 to 50 at %. In addition, a Permalloy or Permender alloy or the like can be used. That is, it is preferable to use a ferromagnetic material having a preferable soft magnetic characteristic.
Preferably, the non-magnetic conductive film is made of Au, Ag or Cu. Further, Cr, Pt, Pd, Ru, Rh or the like, or an alloy thereof can be also used. That is, it is preferable to use a material which does not have spontaneous magnetization at a room temperature and has preferable permeability of electrons. The thickness of each of the above films is preferably about 2 to 1000 xc3x85.
The invention relates to a magnetic head comprising a coil conductor sandwiched by a first magnetic film and a fourth magnetic film, a second magnetic body magnetically coupled with the first magnetic film and a third magnetic body magnetically coupled with the fourth magnetic film, and a magnetic gap sandwiched between the second magnetic film and the third magnetic film. In the structure for realizing both a high frequency characteristic and narrow tracks, which will be described hereinafter, especially to reduce the manufacturing costs, an insulative and non-magnetic film which is exposed to a sliding face includes at least the first magnetic film.
In order to satisfy the fundamental functions of a magnetic head having the above structure, a part of the third magnetic film is exposed to the non-magnetic and insulative film face, and the third and fourth magnetic films are magnetically coupled.
In order to reduce the manufacturing costs of the magnetic head, at least three sides of each of the second and third magnetic films for forming a magnetic gap are surrounded by a non-magnetic and insulative film, on the surface of which a second non-magnetic and insulative film is deposited, and a coil conductor is provided in the second non-magnetic and insulative film.
In order to reduce the manufacturing costs, the second magnetic film and the third magnetic film have the same two-dimensional shape, and a magnetic pole part for specifying a write track width and a back contact part for magnetically connecting the first and fourth magnetic films are constructed in the laminated structure of the second and third magnetic films.
In order to improve the high frequency characteristic, a coil conductor is arranged on the outside of the region, in which the second and third magnetic films exist.
In order to improve the high frequency characteristic, the specific resistance of the first and fourth magnetic films is made higher than that of the third magnetic film.
In order to improve the high frequency characteristic, the volume of the third magnetic film is made 10E-4 or smaller as compared to the volume of the first and fourth magnetic films.
In order to improve the high frequency characteristic and to allow a write magnetic field of the necessary intensity to be generated, the relation of 0.8 less than BS1xc3x97t/Bs2xc3x97Dg less than 1.5 is satisfied, where Bs1 denotes the saturable magnetic flux density of the fourth magnetic film, t the film thickness, Bs2 the saturable magnetic flux density of the third magnetic film and Dg the overlapped length in the floating direction of the third and fourth magnetic films.
In order to reduce the unnecessary write phenomenon to an adjacent track and to realize high density recording, the area of the second and third magnetic films exposed to the air bearing surface of the head is made larger than the area of the first and fourth magnetic films, which are also exposed.
In order to improve the high frequency characteristic, the relation of xcfx81/(xcexcxc3x97t2) greater than 0.0064 is satisfied, where xcfx81(xcexcxcexa9xc2x7cm) denotes a specific resistance of the material used to form the first and fourth magnetic films, xcexc is the relative magnetic permeability at 5 MHz and t (xcexcm) is the film thickness.
A magnetic head, which satisfies the above mentioned condition, is fabricated and a magnetic recording apparatus is assembled by using the magnetic head.
By supplying a control signal at a driving frequency of 150 MHz or higher to a magnetic recording apparatus having a magnetic head with the improved frequency characteristic, the magnetic recording apparatus can be driven at the above driving frequency.
In order to realize high density recording, the width of the third magnetic film exposed to the sliding surface is made 1.0 xcexcm or narrower. In order to satisfy the frequency characteristic and the necessary write magnetic field intensity, the thickness is made 1.0 xcexcm or thinner. Such a magnetic head is fabricated and a magnetic recording apparatus having the magnetic head is assembled.
In order to satisfy the requirements for reliability and the life of a recording apparatus, the first insulative and non-magnetic film as mentioned above is formed of an alumina film or a film containing diamond particles as a main component.
In order to realize both a high frequency characteristic and the necessary write magnetic field intensity, each of the first and fourth magnetic films is composed of a multilayered film, in which a magnetic film and a non-magnetic film are laminated, or a high-electric resistive amorphous alloy film having a specific resistance of 50 xcexcxcexa9xc2x7cm or higher. Further, the third magnetic film is formed of an alloy film whose main component is Coxe2x80x94Nixe2x80x94Fe having a specific resistance of 20 xcexcxcexa9xc2x7cm or lower. Moreover, by mounting the magnetic head having the above structure on a recording apparatus, a high-speed and high- density magnetic recording apparatus is realized.
In order to reduce the manufacturing costs and to improve the frequency characteristic, the first and second magnetic films are made of the same material. By mounting the magnetic head on a magnetic recording apparatus, a high-speed magnetic recording apparatus cab be cheaply manufactured.
In order to realize both a reduction in manufacturing costs and the necessary write magnetic field intensity, the saturable magnetic flux density of the third magnetic film is made higher than that of the second magnetic film. This construction is used under the condition that the third magnetic film is positioned on the side of an outflow end along the rotating direction of a medium with respect to the second magnetic film.